The invention relates to a targetting device for the straight-lined introduction of an instrument into a preferably human body according to the introductory part of claim 1.
With a biopsy, needles are pierced into the body of a patient in order to remove tissue samples from a certain body location or to guide instruments to this location. It is known to locate and fix the target position with the help of a computer tomograph (CT). This produces virtual section images of the body in various sectional planes which usually lie over one another and are transversal. According to the CT-image the target location and the piercing location and thus the course of the piercing channel of the biopsy needle may be fixed. If the piercing cannot be effected perpendicularly from above or from the side because organs or bones lying in this access may not be touched, it is difficult to transfer the course of the piercing channel evaluated by way of the CT images in reality and to guide the long needle at the correct piercing angle. With a deviation from the determined piercing angle one however misses the target location and the procedure must be repeated, or even organs are damaged.
According to DE 92 18 321 there is known a positional indicator which produces at least one light beam directed onto the operation or treatment location on the patient body in order to indicate to the operator the location of operation and where appropriate the operational direction on the body of a patient. The position indicator for this is arranged on the front side of a computer tomograph housing via an arm which can be moved on all sides, with which four arm sections are linked onto one another by three joints. The arm is computer-controlled.
From DE 330 092 there is known a device for positional location of a point for operation technology purposes using a longitudinally displaceable rod as a probe which in a plane is so adjustable at any angle that the tip of the probe coincides with a predetermined point.
DE-OS 195 02 356 describes a targetting device for the straight-lined introduction of an instrument into a human body with a laser light source which is pivotably mounted about a horizontal axis on a carriage, wherein the carriage is adjustably guided and can be fixed along a horizontal guide above the gantry of a computer tomograph.
A computer-controlled device for actuating a position indicator is complicated in many respects. The degrees of freedom of the joints or the bearings of the device must be equipped with sensor technology and drives which permit a computer to recognize the present position and to move into a desired position. The control commands for moving the position indicator must be inputted via the computer in a long-winded manner and in the usual manner there is required a control of the drives in order to achieve positional accuracy.
A rod as an indicator or probe for direction evaluation of an instrument in an operation has the disadvantage that it cannot follow the distance to its holder which becomes larger on introduction of the instrument, it is annoying as a bulky object in an operating region which is any case is quite small, and because one is reliant on an unreliable directional judgement by the eye, only permits a limited accuracy of the directional orientation.
A laser light source as a targetting device, which can be horizontally displaced above the operated-on body and which can be pivoted about a horizontal axis is suitable, limited by the mentioned degrees of freedom, only for guiding an instrument along beams which can be adjusted in a plane fixed by the degrees of freedom.